Scroll type compressors with one stationary or fixed scroll and one orbiting scroll are well known. Scrolls in these compressors have parallel end plates and involute spiral wrap elements of like pitch. The wrap of one scroll makes line contacts with the wrap of the other scroll and also contacts the adjacent end plate to define fluid pockets. As the orbital scroll orbits relative to the fixed scroll, the locations of the contact lines move along the surfaces of the wraps toward the center of the scrolls, the pockets decrease in size compressing the fluid contained in the pockets and the fluid is moved toward the center of the scrolls. A scroll discharge aperture is provided near the center of the fixed scroll to allow compressed fluid to pass from the scrolls into an exhaust cavity. The exhaust cavity is connected to a fluid discharge opening in the compressor housing.
The compressed fluid in the scroll pockets exerts a force on the scroll end plates which tends to separate the end plates. If the scrolls separate too much, the scroll wraps and scroll tip seals will not form a seal with the surface of the end plate of the adjacent scroll. Compressed fluid in one pocket can then move to another fluid pocket that has a lower pressure. An axial thrust assembly is employed to limit axial separation of the scrolls and thereby keep the fluid pockets sealed and maintain compressor efficiency. one common axial thrust assembly includes a plurality of balls in a space between facing surfaces on the compressor housing and on the orbital scroll end plate. These balls transmit the force, exerted on the orbital scroll by compressed fluid in the scroll pockets, from the orbital scroll end plate to the compressor housing and limit axial movement of the scrolls relative to each other.
An anti-rotation assembly is provided to prevent rotation of the orbital scroll. The assembly may include a first ring with a series of apertures that each surround one of the balls and a second ring, identical to the first, that also receives the balls in its apertures. The first ring is fixed to the compressor housing and the second ring is fixed to the orbital scroll. The apertures in the two rings have a diameter which will permit orbital movement of the balls and the orbital scroll and prevent rotation of the orbital scroll.
The compressor drive includes a crankshaft rotatably journaled in the compressor housing. An eccentric bushing is journaled on the crankshaft crank pin. The eccentric bushing is also received in a bore in a boss on the forward wall of the orbital scroll end plate. A bearing is provided in the bore in the boss to allow free rotation of the eccentric bushing relative to the orbital scroll. Scroll compressors are lubricated by lubricant entrained in the fluid they compress. In some designs parts needing lubrication are merely exposed to fluid with entrained lubricant. In other designs lubricant is separated from the fluid and then moved to the parts requiring lubrication.
Lubrication of the eccentric bushing which connects the crankshaft to the orbital scroll is a problem in some compressors. During prolonged high speed operation the bearing which supports the eccentric bushing on the orbital scroll may fail. The journal connecting the eccentric bushing to the crankshaft may also experience rapid wear.